Clinical diagnosis of cancer is a complex process usually initiated by presentation of indicative symptoms. Suspected conditions are identified as possible differential diagnosis and a battery of blood tests, urinalysis, imaging tests, and biopsy are conducted before final diagnosis is made. Biomarkers have been identified for some cancers, but have limited use as a primary screening tool.
Non-Hodgkin's lymphoma (NHL) is a spontaneously occurring neoplasm of particular interest. NHL newly affects 69,740 people annually in the United States (1) and has had a steadily increasing incidence in the United States and Europe (2). If diagnosed early, effective treatments can be selected (2, 3) and the 5 year survival is 72% (1). However, diagnosis is complicated by the lack of a non-invasive test and is presently made by clinical signs, physical examination findings and imaging, with confirmation of disease by biopsy.
Even with effective treatment, 50% of patients with aggressive lymphomas have residual disease and eventually relapse (4). Lymphoma is one of the most commonly encountered canine neoplasms, generally affecting middle-aged to older dogs. Breeds reported to be at increased risk include boxers, bull mastiffs, Bassett hounds, Saint Bernards, Scottish terriers, Airedales, golden retrievers and English bulldogs (6). Typically dogs present with an aggressive high-grade multicenteric lymphoma, of which diffuse large B-cell lymphoma (DLBCL) is the most common subtype (5). Following chemotherapy, 95% all dogs relapse following a period of remission.
While approximately 85% of dogs present with multicentric peripheral lymphadenopathy, a small percentage present with visceral disease only (e.g. primary mediastinal, gastrointestinal or hepatosplenic forms), which requires serial imaging in order to monitor remission status. In humans, remission status is monitored by CT, MRI or PET scans (2). Facile and early detection of relapse may facilitate re-induction of remission and improve outcome.